A library is a set of functions that have been written by someone else already so you don't have to bother. Handy things.

In a C/C++ environment, you normally include a header file into your source code which prototypes the functions, and then link to the library when you build your .exe. Depending on your IDE/software, the linker may do this for you automatically, (most of the time at least).

Wave upon wave of demented avengers march cheerfully out of obscurity unto the dream.